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One room stays cold while the rest of the flat is warm: the floor heating distributor, not the boiler

Korean homes are heated through the floor. The boiler warms water, and a distributor (분배기, sometimes called a manifold) splits that water into one pipe loop per room and collects it again on the way back. When the living room is toasty but the small bedroom never warms up, the boiler has usually done nothing wrong — the trouble is on that room's loop. This page is for the tenant who has already rebooted the boiler twice, the family whose child's room is the cold one, and anyone told by a boiler technician that "the boiler is normal". How to narrow it down in ten minutes, what we fix, and which jobs belong to the boiler maker instead.

Whole flat cold, an error code on the boiler panel, or a gas smell? That is the boiler or the gas line, not the distributor. Call the boiler maker's service line (AS), and for any gas smell stop using the boiler and call your gas supplier first.

Ten minutes before you call anyone

Find the distributor — under the kitchen sink or in the veranda boiler cupboard. Each valve or white cylinder on top feeds one room.
Are all valves open? One room is often shut off in summer and forgotten. If a valve will not turn by hand, leave it — forcing a seized valve can snap the stem and start a leak.
Room thermostat — if each room has its own wall controller, check that the cold room's controller is on and set above the current room temperature.
Boiler pressure gauge — note where the needle sits compared with what you normally see. Low pressure weakens circulation and the farthest rooms go cold first.
Feel the floor — after an hour of heating, walk the cold room barefoot. Warm by the door and cold by the window is a different problem from cold everywhere.

How the room is cold tells us why

Cold from wall to wall, from day one of the season

Valve closed or seized, or the actuator sitting on that valve no longer opens it. Newer apartments with a thermostat in every room have one actuator per loop, and they wear out one at a time.

Warms a little, then a gurgling or trickling sound

Air trapped in the loop. Common at the first heating of autumn and right after any work on the boiler or distributor. Bleeding the air usually brings the room back.

Warm near the door, cold towards the window

Not enough water reaching the end of the loop: the flow on that valve is set too low compared with the other rooms, or rust and sludge have narrowed the old pipe. We rebalance first, then judge whether the loop needs flushing.

One unusually hot patch, and the boiler keeps topping up

This one is different: hot water may be leaking under the floor. If the unit below has a stain on its ceiling as well, it moves to leak detection rather than valve work.

What we do on the visit

1 · Label every loop

We match each valve to its room and label it, because most distributors in rentals carry no labels at all and the next problem is solved faster when they do.

2 · Loosen or replace the valve and actuator

A seized valve is worked loose or replaced; a dead actuator is swapped for a compatible one. If several valves have seized and the bars are crusted with rust, we explain why replacing the distributor may be the better route and you choose.

3 · Bleed and rebalance

Air is pushed out loop by loop, then the flow is shared out so the big room and the small room both get enough, rather than the shortest loop taking it all.

4 · Run it and walk the floor

We run the heating and check the cold room from door to window before we leave, along with every joint on the distributor for drips.

The boiler's power and the heating water are isolated by our technician in the right order before anything on the distributor is opened. We never ask you to operate the gas valve.

What is ours, and what belongs to the boiler maker

Ours: the distributor and its valves and actuators, the heating loops in the floor, bleeding and balancing, flushing sludge out of the loops, hot-water pipes and mixer taps, and finding leaks on the heating side. Not ours: anything inside the boiler casing — burner, heat exchanger, circulation pump, control board, or a leak from inside the boiler. Those go to the maker's service line (AS), and the guide on no hot water explains how to reach them. Gas lines and gas smells go to your gas supplier. Wall thermostats and their wiring are sometimes the maker's job too; we tell you on the spot which side a fault is on.

Price

Fixed quote on site · VAT 10% separate

Depends on whether a bleed and rebalance is enough or valves and actuators are replaced, how many loops the distributor has and how cramped it sits, and whether the loops need flushing. Boiler-internal faults go to the boiler maker's service line.

Fixed quote before work starts — you agree to the number first. If the scope turns out to be different mid-job, we stop and explain before anything continues.
Card payment accepted. Cash receipt or corporate tax invoice (세금계산서) issued on request.
VAT 10% is quoted separately, and we tell you the VAT-included total before starting.

What decides the figure

Bleed and rebalance only, or valves and actuators replaced as well
Number of loops on the distributor, and whether it is cramped inside a sink cabinet
Whether sludge means the loops need flushing after the valves are sorted
Whether a hidden leak has to be located before anything else makes sense

Questions people ask before booking

My landlord says the boiler is fine. So why is the bedroom cold?

Because the boiler only heats the water; the distributor (분배기) decides which room gets it. If the living room is warm, the boiler is doing its job and the problem sits between the distributor and that one room: a valve that has seized half-closed, an actuator on top of the valve that no longer opens it, air trapped in the loop, or sludge narrowing the pipe. That is plumbing work, not boiler work, which is also why a boiler technician sometimes leaves saying everything is normal.

Where is the distributor in a Korean apartment?

In most apartments it sits behind the kickboard or inside the cabinet under the kitchen sink: two horizontal brass or steel bars stacked one above the other, with a row of small valves or white cylinders on top and a pipe running down into the floor from each one. In villas it is often in the boiler cupboard on the veranda, right next to the boiler. Officetels with electric floor heating have none — if you cannot find one, send us a photo of your boiler and the area under the sink.

Can I bleed the air myself?

Many people do. At the end of each bar there is a small bleed screw. Put a towel and a cup under it, open it a quarter turn, let the hiss out, and close it as soon as water appears. Stop and text us if the screw will not turn, if dark red water keeps coming, or if the noise and the cold come back within a few days — that means air is getting in somewhere, usually because the system is losing water, and bleeding again will not fix it.

Is a cold room the landlord's cost or mine?

A valve that has seized with age, a worn actuator or sludge in a decades-old loop is normally treated as the building's wear, so most landlords pay. A setting someone changed is a different conversation. We photograph the distributor before and after and write down what was wrong, which is what usually settles it. The who-pays guide covers the general rules.